It has been known in the art that, compared to certain other classes of polymers, homopolyamides and copolyamides exhibit relatively good gas barrier properties. Typical prior art polyamides are disclosed, for example, in U.S. Pat. No. 4,261,473. Examples of such polyamides include polycaprolactam (Nylon 6), poly-.omega.-aminoheptanoic acid (Nylon 7), poly-.omega.-aminononanoic acid (Nylon 9), polyundecanamide (Nylon 11), polylauryllactam (Nylon 12), polyethylene adipamide (Nylon 2-6), polytetramethylene adipamide (Nylon 4-6), polyhexamethylene adipamide (Nylon 6-6), polyhexamethylene sebacamide (Nylon 6-10), polyoctamethylene adipamide (Nylon 8-6), polydecamethylene adipamide (Nylon 10-6) and polydodecamethylene sebacamide (Nylon 12-10).
Polyamides prepared from aromatic amino compounds are disclosed in U.S. Pat. No. 3,408,334. The aromatic amines used in these polyamides contain amino groups bonded directly to an aromatic ring. Typical examples of suitable diamines are metaphenylenediamine, para-phenylenediamine, isomeric diaminoxylenes, etc. The patent further discloses that p-phenylenedioxydiacetic acid and similar compounds can be employed in the preparation of polyamides.
U.S. Pat. No. 4,482,695 (Barbee et al.) discloses polyamide containers having unexpectedly superior gas barrier properties. Typically these polyamides are prepared from an aliphatic diamine and a dicarboxylic acid which is a diacetic acid. The disclosed polyamides are not of the type employed in the present invention.